ML19263C878

Forwards Addl Info to Support 780313 Application for Amend of Operating License,Revising Proposed Tech Specs & Providing Results of Analytical Work & Field Testing

ML19263C878
Person / Time
Site:	Fort Calhoun
Issue date:	03/06/1979
From:	Short T OMAHA PUBLIC POWER DISTRICT
To:	Reid R Office of Nuclear Reactor Regulation
References
NUDOCS 7903120289
Download: ML19263C878 (8)

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Omaha Public Power District 1023 HARNEY a OMAHA. NEBRASKA 68102 e TELEPHONE 536 4000 ARE A CODE 402 March 6, 1979 Director of nuclear Reactor Regulation ATTl: Mr. Robert W. Reid, Chief Operating Beactors Branch No. 4 U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Re ference : Docket No. 50-285 Gentlemen:

The Omaha Public Power District submitted an Application for Amend-ment of Facility Operating License, dated March 13, 1978, requesting a revision to the surveillance requirements for spent fuel pool area and safety injection pump room ventilation systems. Subsequently, Dis-trict representatives ret with members of the staff on May 16, 1978, to discuss the Application. As a result of that meetinr, please find attached forty (40) copies of additional information to support the Application. The additional information makes a single revision to the previously submitted proposed Technical Specification pages and provides results of analytical work and field testing to support this revision.

Sincerely, I

t' IjY0 y T.Assi'stant E. ShortGeneral Manager p

TES/KJM/BJH:Jmm Attach.

cc: LeBoeur, Lamb, Leiby & MacRae 17 3 "N" Street , H . W .

Washington, D. C. 20036 7 9 0 312 0'c;L&9

TABLE 3-5 .

(Continued)

FSAR Section Test Frec_uency Reference 10b .' Charcoal Adsorbers 1. In-Place Testing ** Each refueling shutdwin not to exceed 18 622 for Spent stel Charcoal adsorbers shall be months or after every 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> of syste= 9.10 Storage Pool Area leak tested and shcl1 show operation, or after each complete or par-299% Freon (R-11 or R-112) tial replacement of the charcoal adsorber removal, bank, or after any major structural mainte-nance on the system housing and f ollowing significant painting, fire or chemical re-lease in a ventilation zone communicating with the system.

2. Laboratory '"esting

a. Initial batch tests of all Prior to initial loading in the filter unit.

charcoal adsorbers shall show >99% elemental iodine >

Y removEl when tested under $

$ conditions of >95% 3.H. , $

1. 21250F, 5 to 10 mg/m3 inlet j elemental iodine concentra- G 6

tion and at the face velocity within +20% of system design.

b. The carbon sample test re- Each refueling shutdown nct to exceed 18 sults shall shov 3.90% ele- months or after every 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> of system mental iodine removal, under operation, and following significant paint-conditions of 295% R.H., ing, fire or chemical release in any venti-3,1250F, 5 to 10 mg/m 3 in- lation zone communicating with the system.

let elemental concentration and within 20% of design face velocity.

3 Overall System Oneration

a. Operation of each circuit Ten hours every month, shall be demonstrated.

b. Volume flow rate through At least once per plant operating cycle.

charcoal filter shall be shown to be between 9000 and 12,000 cfm.

h. Manual initiation of the syst- At least once per plant operating cycle.

shall be demonstrated.

• • Tests shal? be performed in accordance with applicable section(s) of ANSI N510-1975 AmendmentNo.[,2h

TABLE 3-5 -

(Continued)

FSAR Sectica Test Frecuency Reference 10c. Charcoal Adsorters 1. In-Place Testing ** Each refueling shutdown not to exceed 18 9 10 for S.I. Pump Roon Charcoal adsorbers shall be months or after every 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> of syste= 6.2 leak tested and shall show operation or after each complete or partial

>997 Freon (R-ll or R-ll2) replacement of the charcoal adsorber bank, renoval. or after any najor structural maintenance on the system housing and folleving signi-ficant paiting, fire or chemical release in any ventilation zone connunicating with the system.

2. Laboratory Testing

a. Initial batch tests of all Prior to initial loading in the filter unit.

charcoal adsorbers shall shov >p9% elemental iodine w

a removal when tested under m conditions of >95% R.H.,

O >1250F, 5 to 10 ng/m3 in-let elemental iodine con-centration and at a face velocity within +20% of systen design.

b. The carbon sample test Each refueling shutdown not to exceed 18 results for the S.I. Pump months or after every 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> of system Room charcoal filters shall operation and following significant paint-show no less than 90% ele- ing, fire or chemical release in any venti-cental iodine renoval, lation zone cot =unicating with the system.

under conditions of >95%

R.H. t >125 F, 5 to 10 tc/ns$ a -- elenental inlet icdine concentration and within +20% of design face velocity.

3 Overall systen oneration

a. Operation of each circuit Ten hours every month.

shall be demonstrated.

b. Volume flow rate shall be At least once per plant operating cycle.

shown to be between 3000 and o000 cfn.

• • Tests shall be performed in accordance with applicable section(s) of ANSI N510-1975 Anendment No. y[, 2h

DISCUSSIO:I Section 910 of the Fort Calhoun Station Unit No. 1 FSAR discusses the design function of the charcoal filters which are installed in the con-trolled access area ventilation system:

" Charcoal filters are installed in normally bypassed ducts at the exhaust of the three compartments where the safety injection and spray pumps and suction piping are situated. These filters could be remote-manually brought on to line in the event of an accidental release of activity in these rooms during a plant emergency in particular during the recirculation period following a DBA (see Section 6.2)."

"A charcoal filter is also installed in a normally bypassed section of the return ductwork drawing air from the spent fuel storage pool area.

During spent fuel handling, the filter will be brought on the line to absorb gaseous iodines in the unlikely event of a fuel handling incident resulting in the release of large quantities of radioactivity (Section Ih.18)."

Design flow rates for the two safety injection / spray pump room fil-ters and for the spent fuel storage pool area filter are 5500 cfn per filter and 12,800 cfm, respectively. However, although the ventilation system at Fort Calhoun Station has been adjusted for optimum performance, the design flow rates have not been achieved. The maximum flow rates obtainable without extensive modification of the ventilation system are hh00 cfm for each safety injection / spray pump room filter and 10,h00 cfm for the spent fuel storage pool area filter.

The FSAR does not describe in detail the basis for the design air flow rates. The District attempted to obtain the design calculations from the architect / engineer, but found that the necessary documents were unavailable. It is, therefore, the intention of the District to provide herein a basis for the proposed air flow rates.

The controlled area exhaust system is composed of a network of ex-haust grilles and ductwork which merge at a common discharge stack. In the safety injection / spray pump rooms and spent fuel storage pool area, the potential exists for relatively high iodine concentrations during accident condition 3. Charcoal filters are installed to allow reduction of these iodine concentrations before the air is released to the dis-charge stack. The iodine concentration at the site boundary is related to the rate of flow through the charcoal filters in the following ways:

(1) 1he spent fuel storage pool area charcoal filter unit contains 12 charcoal filter cells rated at 1000 cfm each. Each safety injection / spray pump filter contains 6 charcoal filter cells rated at 1000 cfm each. As the flow rate becomes greater than design, the adsorption efficiency of the filter decreases.

(2) The air flowing through the charcoal filters is diluted by air from other portions of the controlled access area, prior to being released through the exhaust stack. Only the air passing through the charcoal filters would contain appreciable amounts of iodine. Thus, as the ratio of filtered air to dilution air increases, the concentration of iodine released from the stack also would increase.

(3) All exhaust grilles near the spent fuel pool are located up-stream of charcoal filter unit VA-66. The ventilation system ensures that any radioactive releases from the spent fuel pool vould be filtered prior to discharge from the building.

It is clear that items (1) and (2) would be adversely affected by flow rates through the charcoal filters greater than design. Conversely, flow rates below design vould have a favorable effect upon (1) and (2).

Regarding item (3), the ventilation system was designed to ensure that any releases from the spent fuel pool vould pass through filter unit VA-66 prior to exiting the plant. Supply air is introduced at a level below and adjacent to the spent fuel pool, suceps across the spent fuel pool, and is exhausted through nearby grilles. The air is then directed through VA-66 prior to discharge from the plant; the nearest non-filtered duct is approximately 80 feet away from the spent fuel pool. Thus, ef-fective filtration of any releases frcm the spent fuel pool would be assured even at very lov exhaust flow rates.

The safety injection pump rooms are supplied with water-tight doors which, being normally closed, would preclude the uncontrolled release of contaminated air from the rooms. Ventilation is via ducted supply and ducted, filtered exhaust. Testing performed by the District indicated that, with hh00 cfm per room and the doors open approximately 20%, air flowed from the corridor into the rooms.

One purpose of the safety injection pump room ventilation system is to provide adequate cooling for the safety injection / containment spray pump motors. The District has developed a numerical model for determining pump room temperature as a function of time. The develop-ment of this numerical solution proceeded as follows.

Heat flow in the room was attributed to heat generation by the motors, convection to/from piping, and convection to the valls, or 9 motor " 9 walls + 9 piping In order to allow determination of the room temperature during the tran-sient period, a series of finite difference equations was written for each vall, yielding:

P Eq. 1-1 ,!4 Cp,A(Tpoog A - To) = h oA(To - T l) + hpp A (To - Tp )

A0 Eq. 1-2 To - Ty + KA(Tp - T l) = M CP C ,C(T l -T) I Ax A0 Eq. 1-3 3 A + J+' - 3 = MCPC ,C(Tj l -T)3 Ax Ax A0 Eq. 1-h KA(Tn Tn ) + 1% A(Too - Tn) = ' " "

Ax A0 where:

q = Motor heat, Btu /hr 14A = Macs of air in room, lbm IIC + Concrete Cp, A = Sp. heat of air, Btu /lba - F CP ,C + Concrete A0 = Time increment, hr T R00.1 = Room temp. after 60, OF To = Current room temp., OF ho = Cony. H.T. coer. inside 'rocn, Btu /hr-ft 2_op T1 = Temp. G N0DE 1l, F Tj = Temp . @NODEJ,OF Current T = _

S = Temp. O NODE p, OF Indicates temp. after A0, OF T

Too = Temp. outside of wall, F hoo = Conv. H.T. coef, outside room, Btu /hr-ft 2_op hp = Conv. H.T. coef. for pipe, Btu /hr-ft 2_op ,

Ap = Area of pipe, ft Tp = Temp. of pipe, OF A = Area of vall, ft2 K = Cond. H.T. coer, for concrete , Btu /hr-ft- F The equal.lonc vere then manipulated into a suitable forn to allow solution on a digital computer. For comparison, a closed-form analytical solutien was obtained from the literature.1 Thic solution providen a method for quantifying the transient temperature of air in an enclosure with heat lascen, a situation very near]y identical to that which occurs in the safety injection pump rooms. The numerical solutien correlated very elocely with this analytical solution over the entire time interval investi Cated, with a maxinum calculated error of less than 17..

The District had performed a test program during February and November of 1978 with the intention of measuring pump room temperatures. The first test program had been performed with all four pumps in one room operating at minimum (recirculation) flow; the second test program had been performed with the two safety injection pumps operating at design flow and the two containment spray pu:q)s operating at minimum (recirculation ) flow. In both of these test programs, room temperatures were measured at selected time intervals folleving stnrtup of the pumps. As expected, the temper-ature increased more rapidly in the latter case, since the pump motors were more heavily loaded.

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h-These test results were used as an additional check for the numerical solution. When compared with actur.' test data, the numerical solution predicted a higher room temperature over the first 10 to 15 mirutes, after which the results correlated quite well, with an error of 3.9% at 50 minutes.

Finally, the numerical solution was used to compute temperatures for anticipated post-LOCA conditions. These conditions were assumed as fol-lows:

(1) initial room temperature of 95oF; (2) steady-state temperature of 95oF in balance of auxiliary build-ing; (3) initial concrete temperatures of 95.0 to 65 0oF, depending upon location; (h) full-load operation of four pumps per room for first 30 minutes after the LOCA; (5) full-load operation of three pumps per room for time greater than 30 rdnutes; (6) pipe temperature equal to SIRWT temperature prior to RAS, equal to sump temperature after RAS; (7) ventilation flow rate of 3000 cfm per room at 95 F; (8) the heat contribution of fluid leakage is insi 6nificant; (9) pump motor efficiency of 92%;

(10) convection heat transfer coefficients of (a) 3.6 Btu /hr-ft2 _oF for intental valls (b) 2 9 Btu /hr-ft2 oF for internal floors (c) 2 _oF for ceiling

h. 0 Btu /hr-ft (d) 1.7 Btu /hr-ft2 - F for piping (e) .10 Btu /hr-ft2 _oF for surfaces in contact with ground;

(' conductien heat transfer coefficient of 1.05 Btu /hr-ft- F; and (12) Bround temperature of 550F.

The bearings for the safety injection / containment spray purp motors are the limiting factors in determining the maxinum allovable roon tem-perature. The nuluracturer has recommended that the motors not be operated with room ambient temperatures greater than 122oF. The tuinlysis performed by the Dintrict indicates that, under the postulated post-LOCA conditions, a room temperature of 1220F would be reached approximate]y 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> after the accident. However, long before this time sufficient decay heat would be removed that one safety injection pump would sufficiently cool the re-actor core. 3000 cfm would be adequate to maintain the room temperature below 122oF indefinitely if only one or two pumps were operating.

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It is emphasized, however, that the numerical analysis conservatively assumes operation of three pumps per room for all time greater than 30 cdnutes.

Based upon the analyses and test program discussed above, it is the District's position that the proposed Technical Specification revisions will ensure operability of the auxiliary building ventilation system.

The proposed flov rates for the spent fuel pool area charcoal filter unit are adequate to provide filtration of any releases from the spent fuel pool. The proposed flow rates for the safety injection pump rooms are suffielent to maintain a satisfactory operating environment for the safety injection / containment spray pumps.

This proposed Technical Specification revision does not constitute an unreviewed safety question as defined by 10 CFR 50.59. The probability of an accident or malfunction of equipment is not increased; the reliability of the ventilation system is unchanged, and the proposed flow rates are adequate to maintain operability of the ventilation system. Jhe Technical Specifications do not define a margin of safety for this system.

bolfe, W. A. , " Transient Response of Heated Air in an Enclosure With Heat Losses", Journal of Heat Transfer, February 1959

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